On 04/01/18 12:02, Mark Brown wrote:

On Wed, Jan 03, 2018 at 09:20:45AM -0800, Stephen Boyd wrote:

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On 12/14/2017 09:34 AM, srinivas.kandagatla@linaro.org wrote:

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uThis patch adds support to DB820c machine driver.

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+	ret = dma_coerce_mask_and_coherent(card->dev, DMA_BIT_MASK(32));

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Why do we need to do this? Can you add some sort of comment in the code
about why?

And why are we applying DMA restrictions in a machine driver?

Initially I had this in pcm driver, but looking at example usage of 
snd_dma_alloc_pages, most of them use card->dev and some of them use pcm 
device for allocating dma memory.

Also, as I moved most dsp static services and dais out of DT, except 
codec and sound card, sound card device was the only choice I had for 
binding with iommu and enforcing iova range restrictions.

This call will be replaced by dma-ranges property in DT either way.


--srini